Stowaway skinks help solve human history mystery

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Tiny skinks, whose ancestors stowed away on rafts with the earliest Pacific navigators, are helping unravel the mystery of how humans first colonised the Pacific region.

Adelaide scientists have been studying the DNA of the lizard species Lipinia noctua, which is found throughout the Pacific and is thought to have spread with humans on the canoes, outriggers and rafts that they used to settle the region.

Anthropologists have been unable to agree how humans first colonised the Pacific, but the scientists from the South Australian Museum reasoned that if they could plot the migration patterns of the skinks, it should also reflect patterns of human migration.

"Before we did this work, all the theory was based on humans," said Dr Stephen Donnellan, from the South Australian Museum. "This is a completely different tack."

There are two conflicting theories to explain Pacific settlement: The 'entangled bank theory', proposing slow migration, and the 'express train theory', which argues settlement happened in a single fast wave. DNA analysis of the skink populations suggested the lizards spread relatively rapidly, in support of the express train model. Their results were reported recently in the scientific journal Nature.

Dr Christopher Austin said the lizards are all so similar that they can be traced back to a common point of origin - most probably the Solomon Islands.

Dr Donnellan doubts the skinks had any trouble stowing away on the large Polynesian outriggers. "The lizards were quite at home on logs and would have been quite at home on canoes."